Conductive polymeric coatings and methods

ABSTRACT

Embodiments of the invention include conductive polymeric coatings and methods of making the same. In an embodiment, the invention includes a method of electrodepositing a conductive polymeric coating onto a substrate surface. The method can include contacting the substrate surface with a solution comprising a monomer, a counterion, and a solvent; exposing the solution to an electrical potential, wherein the surface serves as an electrode in the application of the electrical potential; and alternating the electrical potential between a lower potential and a higher potential to form the conductive polymeric coating on the substrate surface. Other embodiments are also included herein.

This application claims the benefit of U.S. Provisional Application No.61/860,683 filed Jul. 31, 2013, the contents of which are hereinincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to conductive polymeric coatings andmethods of making the same.

BACKGROUND OF THE INVENTION

While many polymers are strong electrical resistors, it will beappreciated that there also various electrically conducting polymers.Such polymers have many applications in electronics, medicaltechnologies and general industrial settings. By way of example, variousconductive polymers have been applied as coatings over substrates.

SUMMARY OF THE INVENTION

Embodiments of the invention include conductive polymeric coatings andmethods of making the same. In an embodiment, the invention includes amethod of electrodepositing a conductive polymeric coating onto asubstrate surface. The method can include contacting the substratesurface with a solution comprising a monomer, a counterion, and asolvent; exposing the solution to an electrical potential, wherein thesurface serves as an electrode in the application of the electricalpotential; and alternating the electrical potential between a lowerpotential and a higher potential to form the conductive polymericcoating on the substrate surface.

In an embodiment, the invention includes a device including a substrateand a conductive polymeric coating disposed over the substrate, whereinthe conductive polymeric coating exhibits a durability that is greaterthan an otherwise compositionally identical conductive polymeric coatingformed by a potentiostatic deposition or galvanostatic method.

This summary is an overview of some of the teachings of the presentapplication and is not intended to be an exclusive or exhaustivetreatment of the present subject matter. Further details are found inthe detailed description and appended claims. Other aspects will beapparent to persons skilled in the art upon reading and understandingthe following detailed description and viewing the drawings that form apart thereof, each of which is not to be taken in a limiting sense. Thescope of the present invention is defined by the appended claims andtheir legal equivalents.

BRIEF DESCRIPTION OF THE FIGURES

The invention may be more completely understood in connection with thefollowing drawings, in which:

FIG. 1 is a schematic diagram of a system for coating a substrate inaccordance with an embodiment herein.

While the invention is susceptible to various modifications andalternative forms, specifics thereof have been shown by way of exampleand drawings, and will be described in detail. It should be understood,however, that the invention is not limited to the particular embodimentsdescribed. On the contrary, the intention is to cover modifications,equivalents, and alternatives falling within the spirit and scope of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention described herein are notintended to be exhaustive or to limit the invention to the precise formsdisclosed in the following detailed description. Rather, the embodimentsare chosen and described so that others skilled in the art canappreciate and understand the principles and practices of the presentinvention.

All publications and patents mentioned herein are hereby incorporated byreference. The publications and patents disclosed herein are providedsolely for their disclosure. Nothing herein is to be construed as anadmission that the inventors are not entitled to antedate anypublication and/or patent, including any publication and/or patent citedherein.

As described above, electrically conducting polymers have manyapplications in electronics, medical technologies and general industrialsettings. As one example, relevant to medical technologies, electricallyconducting polymers have been applied over portions of medical devicessuch as over electrodes, sensors, cases, or the like.

However, it has been observed that electrically conducting polymers whenapplied as coatings may exhibit durability that is less than desirablefor some applications. For example, it has been observed that theapplication of frictional force to the surface of some electricallyconductive polymeric coatings can result in portions of the coatingcoming off the surface to which the coating was disposed on. In somecases, the entire coating may come off.

Embodiments herein include electrically conductive polymeric coatingsthat exhibit improved durability. Embodiments herein also includemethods of electrodepositing conductive polymeric coatings ontosubstrates.

In an embodiment, a method of electrodepositing a conductive polymericcoating onto a substrate surface is included. The method can includecontacting the substrate surface with a solution comprising amonomer(s), a counter ion and a solvent.

The monomer can include one or more distinct monomers. The monomer(s)can include those that polymerize to form an electrically conductivepolymer. In some embodiments, the monomer can include3,4-ethylenedioxythiophene. In some embodiments, a counter ion can alsobe included. In some embodiments, the counter ion can include apolystyrenesulfonate salt. In some embodiments, the monomer comprises amixture of 3,4-ethylenedioxythiophene and a counter ion ofpolystyrenesulfonate salt. It will be appreciated that beyond themonomer, suitable counter ion and a suitable solvent, the solution canfurther include various other components including, but not limited to,additional monomers, additives, salts, co-solvents, and the like

The molar ratios of the monomer and the counterion can be varieddepending on the desired end properties of the coating. By way ofexample, in some embodiments, the ratio of 3,4-ethylenedioxylthiopheneto polystyrenesulfonate can vary from 1:2 to 2:1. In yet other exemplaryembodiments, the ratio of 3,4-ethylenedioxylthiophene topolystyrenesulfonate can be 1:1.

In some embodiments, the resulting conductive polymeric coatingcomprises poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)(PEDOT:PSS).

The substrate surface can include various materials. In someembodiments, the substrate surface includes an electrically conductivematerial. In some embodiments, the substrate surface comprising a metal.In some embodiments, the substrate surface comprising platinum. In someembodiments, the substrate surface comprises platinized stainless steel(stainless steel coated with platinum). In some embodiments, thesubstrate surface comprises platinum-iridium such as platinum-iridium(90:10). In some embodiments, the surface can be textured and in otherembodiments the surface can be substantially smooth.

The method can also include exposing the solution to an electricalpotential, wherein the surface serves as an electrode in the applicationof the electrical potential. The method can also include alternating theelectrical potential between a lower potential and a higher potential toform the conductive polymeric coating on the substrate surface.

In some embodiments, alternating the electrical potential between alower potential and a higher potential comprises changing the electricalpotential in a step change pattern. The step change pattern can includea single change from the lower potential to the higher potential, orfrom the higher potential to the lower potential. In other embodiments,the step change pattern can include multiple incremental changes fromthe lower potential to a higher potential, or from the higher potentialto a lower potential.

In some embodiments, alternating the electrical potential between alower potential and a higher potential comprises changing the electricalpotential gradually at a particular rate of change. It will beappreciated that various rates of change can be used. In someembodiments, the rate of change is from about 5 mV/s to about 200 mV/s.In some embodiments, the rate of change is from about 20 mV/s to about100 mV/s. In some embodiments, the rate of change is from about 40 mV/sto about 60 mV/s. In some embodiments, the rate of change is from about45 mV/s to about 55 mV/s. In some embodiments, the rate of change isabout 50 mV/s.

In some embodiments, the lower potential is between −1.5 V and 1.0 V. Insome embodiments, the lower potential is between −0.5 V and 0.7 V. Insome embodiments, the lower potential less than about 0.7 V. In someembodiments, the lower potential less than about 0 V. In someembodiments, the lower potential is about −0.2 V.

In some embodiments, the higher potential is between 0.5 V and 3.0 V. Insome embodiments, the higher potential is between 0.7 V and 2.0 V. Insome embodiments, the higher potential is between about 1.0 V and 1.6 V.In some embodiments, the higher potential is between about 1.2 V and 1.5V. In some embodiments, the higher potential is about 1.4 V.

In some embodiments, alternating the electrical potential comprisesalternating the electrical potential between the lower potential and thehigher potential a plurality of times. In some embodiments, alternatingthe electrical potential comprises alternating the electrical potentialbetween the lower potential and the higher potential from between 1 and500 times. In some embodiments, alternating the electrical potentialcomprises alternating the electrical potential between the lowerpotential and the higher potential from between 2 and 200 times. In someembodiments, alternating the electrical potential comprises alternatingthe electrical potential between the lower potential and the higherpotential from between 10 and 50 times.

In yet other embodiments, a combination of potentiostatic andpotentiodynamic processes can be alternatingly applied to ultimatelyachieve durable coated surface properties. By way of example, apotentiostatic (constant voltage) process could be used first followedby a potentiodynamic process. Alternatively, a potentiodynamic processcould be used first followed by a potentiostatic process. In someembodiments, a method can include alternating between potentiostatic andpotentiodynamic processes.

In some embodiments, further operations can be performed after initialdeposition of the electrically conductive polymeric coating. By way ofexample, in some embodiments, an additional coating layer, such as a topcoat, can be applied. In other embodiments, various compounds can beapplied in order to improve properties of the coating such as, but notlimited to, the conductivity of the coating.

Coatings in accordance with embodiments herein can exhibit superiorproperties in comparison to otherwise similar or compositionallyidentical coatings that are applied in different ways. By way ofexample, in some embodiments, the conductive polymeric coating adheresmore strongly than an otherwise compositionally identical polymericcoating formed by a potentiostatic or galvanostatic application method.In some embodiments, the conductive polymeric coating exhibits aresistance to frictional removal that is greater than an otherwisecompositionally identical polymeric coating formed by a potentiostaticor galvanostatic application method. In some embodiments, the conductivepolymeric coating exhibits a durability that is greater and aconductivity that is lower than an otherwise compositionally identicalpolymeric coating formed by a potentiostatic or galvanostaticapplication method.

Referring now to FIG. 1 a schematic diagram of a system 100 for coatinga substrate in accordance with an embodiment herein is shown. The system100 includes a container 102 into which components of the system can beplaced. A substrate 104 is shown with a conductive polymeric layer 106disposed thereon. A solution 108 is in contact with the substrate 104and/or the conductive polymeric layer 106. The system 100 also includesan electrode 110 for applying the electric potential. The substrate 104itself can serve as the other electrode. The system 100 can also includea controller 112 for applying the electric potential as describedherein. In some embodiments, the controller 112 can be apotentiostat/galvanostat.

The present invention may be better understood with reference to thefollowing examples. These examples are intended to be representative ofspecific embodiments of the invention, and are not intended as limitingthe scope of the invention.

EXAMPLES Coated Rod Durability Test Method

This test method was developed to compare the durability of coatings ona cylindrical rod. A texture analyzer system (model TA XT Plus,available from Stable Microsystems, Godalming, Surrry, UK) equipped witha load cell was used to control the speed and distances. The platinumcoated stainless steel rod to be tested (3″ length×0.125″ diameter) wasplaced in a hemostasis valve with a silicone compression seal(hemostasis Valve Y Connector; part No. 80398, available from QosinaInc, Edgewood, N.Y.). The diameter of the hemostasis valve allows foruniform force to be applied to the circumference of the coatedcylindrical sample rod to be tested.

The tests were performed using a fluid circulation system adapted to thehemostasis valve. The hemostasis valve was modified with a fitting onthe sidearm and exit. Tubing was attached to the fittings and theopposite ends were positioned in a fluid reservoir. A peristaltic pumpwas then placed between the reservoir and sidearm port to deliver fluidto the hemostasis valve returning to the reservoir via the exit port.Fluid was recirculated continuously throughout the test run with novisible leaks at the compression fitting when fluid pressure was appliedon the test part.

Example 1 Potentiodynamic Deposition of Conductive Polymeric Layer

All electrochemical experiments were carried out using SP-150potentiostat/galvanostat (BioLogic). The electrochemical cell was aconventional three-electrode system with a platinum mesh as the counterelectrode and Ag/AgCl/KCl (3.5M) as the reference electrode.

Platinum-coated stainless steel rods (3″, ⅛″, matte finish) were used assubstrates. The area 0.5″ from the top was not coated (i.e., only 2.5″of the rod was coated).

The solution used for polymerization contained3,4-ethylenedioxythiophene (0.25 mL) and sodium polystyrene sulfonate (1g) in 250 mL of water. Potentiodynamic polymerization was carried out bycycling in the potential range from −0.2 to 1.4 V at scan rate of 50mV/s (20 cycles). Potentiostatic electrodeposition was performed withseveral voltages: 1.1, 1.2, 1.3 and 1.4 V for 10 min. Duringgalvanostatic polymerization 2, 3, 5 and 10 mA current was used for 10min.

During potentiostatic (1.2, 1.3 and 1.4 V) and galvanostatic (3, 5 and10 mA) electrodeposition dark-blue precipitate started to form aroundthe working electrode after about 3 min and settled to the bottom. Noprecipitate formed during potentiodynamic method or at 1.1 V or at 2 mA.

The resulting coatings were rinsed with DI water and tested fordurability by using the test method described above. The durability wasassessed qualitatively.

The coatings deposited by potentiodynamic method appeared to be the mostdurable and uniform.

It should be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the content clearly dictates otherwise. Thus, for example,reference to a composition containing “a compound” includes a mixture oftwo or more compounds. It should also be noted that the term “or” isgenerally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

It should also be noted that, as used in this specification and theappended claims, the phrase “configured” describes a system, apparatus,or other structure that is constructed or configured to perform aparticular task or adopt a particular configuration to. The phrase“configured” can be used interchangeably with other similar phrases suchas arranged and configured, constructed and arranged, constructed,manufactured and arranged, and the like.

All publications and patent applications in this specification areindicative of the level of ordinary skill in the art to which thisinvention pertains. All publications and patent applications are hereinincorporated by reference to the same extent as if each individualpublication or patent application was specifically and individuallyindicated by reference.

The invention has been described with reference to various specific andpreferred embodiments and techniques. However, it should be understoodthat many variations and modifications may be made while remainingwithin the spirit and scope of the invention.

1. A method of electrodepositing a conductive polymeric coating onto asubstrate surface comprising: contacting the substrate surface with asolution comprising a monomer, a counter ion, and a solvent; exposingthe solution to an electrical potential, wherein the surface serves asan electrode in the application of the electrical potential; andalternating the electrical potential between a lower potential and ahigher potential to form the conductive polymeric coating on thesubstrate surface.
 2. The method of claim 1, wherein alternating theelectrical potential between a lower potential and a higher potentialcomprises changing the electrical potential in a step change pattern. 3.The method of claim 1, wherein alternating the electrical potentialbetween a lower potential and a higher potential comprises changing theelectrical potential gradually at a particular rate of change.
 4. Themethod of claim 3, wherein the rate of change is from about 5 mV/s toabout 200 mV/s.
 5. (canceled)
 6. (canceled)
 7. The method of claim 3,wherein the rate of change is from about 45 mV/s to about 55 mV/s. 8.(canceled)
 9. The method of claim 1, wherein the lower potential isbetween −1.5 V and 1.0 V.
 10. The method of claim 1, wherein the lowerpotential is between −0.5 V and 0.7 V.
 11. (canceled)
 12. (canceled) 13.(canceled)
 14. The method of claim 1, wherein the higher potential isbetween 0.5 V and 3.0 V.
 15. The method of claim 1, wherein the higherpotential is between 0.7 V and 2.0 V.
 16. (canceled)
 17. (canceled) 18.(canceled)
 19. (canceled)
 20. (canceled)
 21. (canceled)
 22. The methodof claim 1, wherein alternating the electrical potential comprisesalternating the electrical potential between the lower potential and thehigher potential from between 10 and 50 times.
 23. The method of claim1, the monomer comprising a monomer that polymerizes to form anelectrically conductive polymer.
 24. The method of claim 1, theconductive polymeric coating comprising poly(3,4-ethylenedioxythiophene)and poly(styrenesulfonate) (PEDOT:PSS).
 25. The method of claim 1, themonomer comprising 3,4-ethylenedioxylthiophene.
 26. The method of claim1, the counter ion comprising a polystyrenesulfonic acid or saltthereof.
 27. The method of claim 1, the monomer comprising3,4-ethylenedioxylthiophene and the counter ion comprising apolystyrenesulfonate salt.
 28. The method of claim 1, the solutionfurther comprising an additive.
 29. The method of claim 28, the additivecomprising sodium dodecyl sulfate.
 30. (canceled)
 31. (canceled) 32.(canceled)
 33. (canceled)
 34. The method of claim 1, the substratesurface comprising a metal.
 35. (canceled)
 36. (canceled)
 37. A devicecomprising: a substrate; a conductive polymeric coating disposed overthe substrate; wherein the conductive polymeric coating exhibits adurability that is greater than an otherwise compositionally identicalconductive polymeric coating formed by a potentiostatic or galvanostaticdeposition method.
 38. The device of claim 37, the conductive polymericcoating comprising PEDOT:PSS.